1. Field of the Invention
The present invention relates to a side-looking type endoscope which allows a manipulating tool to be inserted thereinto and, more particularly, to the structure of a side-looking type endoscope which leads a manipulating tool from the end portion toward the side surface of the endoscope.
2. Description of the Related Art
Electronic endoscopes having a charge coupled device (CCD), which is a solid-state image sensor, at the end portion and endoscopes for observing an image only by an optical means are conventionally known. Such an endoscope is not only used to observe the internal state of the body as the object of inspection but also used together with a manipulating tool such as forceps for the purpose of incision, biopsy and collection.
FIG. 11 shows the structure of the end portion of a conventional side-looking type electronic endoscope. In the side-looking type electronic endoscope, a forceps insertion hole 3 which communicates with the manipulating tool insertion channel 2, namely, a part of a manipulating tool insertion channel 2, an observation window (not shown), an irradiation window (not shown), etc. are provided not on the front surface but on the side surface of the end portion 1 of the endoscope. A CCD 4, which is a solid-state image sensor, is provided slightly above the middle portion in the endoscope. The CCD 4 picks up the image which is observed through the observation window. Through the side-looking type endoscope, it is therefore possible to observe and treat a diseased part which lies in the orthogonal direction relative to the direction of insertion of a manipulating tool.
A raising table 5 which rotates toward the forceps insertion hole 3 is attached to the side surface (at the lower portion) of the end portion 1 of the endoscope, and a wire 7 is connected to the raising table 5. The wire is also connected to an operating portion. By pulling the wire 7, the raising table 5 is rotated, thereby raising a manipulating tool 8, which is led out through the forceps insertion hole 3, up to a predetermined position, as indicated by the broken line. In this case, an arcuate groove 9 for guiding the manipulating tool 8 is formed in the raising table 5 so as to ensure the operation of bending the manipulating tool 8. Examples of the manipulating tool 8 are biopsy forceps, sterilizing forceps, high-frequency knife, high-frequency snare, high-frequency hemostatic tool, cytodiagnostic brush and injection needle. Various treatments are carried out while bending these manipulating tools 8.
A conventional endoscope, however, suffers from a problem that the smooth movement of the manipulating tool 8 is difficult in the state of being bent by the raising table 5. More specifically, the arcuate groove 9 formed in the raising table 5 in such a manner as to be engaged with the manipulating tool 8 has a gently curved bottom line, as shown in FIG. 12, so that, in the state in which the raising table 5 is erect, the raising table 5 comes into contact with the manipulating tool 8 at a point A of the arcuate groove 9. At this time, since the manipulating tool 8 is bent at a large angle, the force applied to the manipulating tool 8 for moving the manipulating tool 8 does not act effectively thereon, thereby making a smooth movement of the manipulating tool 8 impossible. Recently, the angle at which the manipulating tool 8 is bent has a tendency of being increased, and a measure for enabling a smooth movement of the manipulating tool 8 is demanded.
In a conventional endoscope, it is impossible to bend the manipulating tool 8 at the forceps insertion hole 3, which is the exit passage of the manipulating tool insertion channel 2, at a large angle. Since the manipulating tool insertion channel 2 is composed of a circular pipe, the section of the forceps insertion hole 3 at the exit passage of the manipulating tool insertion channel is also circular (round). In addition, since the forceps insertion hole 3 is provided obliquely in a straight line, it is difficult to bend the manipulating tool 8 at a large angle.
It is further desired that the curvature radius of the curve formed by bending the manipulating tool 8 should be large. It is because if the curvature radius of the curve is small, the load applied to the manipulating tool 8 in the erect state becomes large, which prevents the functional operation of the manipulating tool 8 and shortens its life.
The curvature radius of the manipulating tool 8 and the angle at which the manipulating tool 8 is bent are not large in a conventional endoscope partly because it is impossible to incline the passage of the forceps insertion hole 3 at a large angle due to the presence of the CCD 4, so that the inclination of the forceps insertion hole 3 is gentle. As shown in FIG. 13, an observation window 52 is attached to the CCD 4 through an optical lens 51. The observation window 52 must be close to the forceps insertion hole 3 because the diseased part is treated while it is being observed. Therefore, the inclination of the forceps insertion hole 3 is determined with due consideration for the position of the CCD 4. In a conventional endoscope, however, the CCD 4 is disposed in the upper region of the endoscope which is the region where the manipulating tool insertion channel 2 is extended, as shown in FIG. 11, so that the presence of the CCD 4 limits the inclination of the forceps insertion hole 3, thereby making it impossible to allow the manipulation tool 8 to have a large curvature radius and to be bent at a large angle.